In most small arms-type firearms, such as handguns, shotguns and various other types of long guns including lever action and semiautomatic rifles, the firearm trigger assemblies or fire control systems thereof generally include a hammer that is held in a cocked position by a mechanical interface with a sear. The sear is connected either directly or through mechanical linkages to the trigger of the firearm. When the trigger is squeezed or moved rearwardly to fire a round of ammunition, the sear generally is moved out of locking engagement with the hammer so as to release the hammer. The hammer then is pivoted into contact with a firing pin of the firearm by a hammer spring. The engagement of the firing pin by the hammer causes the firing pin to strike a round of ammunition in the chamber of the firearm to initiate the firing of the round of ammunition.
In a conventional hammer sear interface, the sear typically includes a notched, hooked portion that engages a corresponding notch or hook formed in the rear hammer. Due to the sliding nature of this mechanical interface, the sear and hammer generally must be precisely machined so as to provide and ensure smooth and even surfaces on both the hammer and sear. This precise machining also provides a smooth and crisp trigger feel during shooting to avoid catching or hesitation during firing, which can lead to misfires and affect the aim of the shooter. The criticality of the components returning to full engagement upon release of the trigger thus further requires that the geometry and surface finishes of the hammer and sear be carefully and somewhat precisely machined and finished, such that the hammer and sear will regain full engagement in such a situation in which the trigger is released after a partial trigger pull without firing. Such precise and careful machining of these components, however, generally is expensive and requires significant quality control and review to ensure that such parts are precisely machined to within specific, narrow ranges of tolerances necessary to provide a smooth interface and function.